The invention disclosed herein is related to the technology disclosed in U.S. Pat. No. 4,917,477, which is owned by the assignee of the present invention, and the aforesaid U.S. patent is to be considered incorporated herein by reference.
Recent advances in electronic technology, particularly the packaging of modules into smaller spaces, has the automobile manufacturers requesting more information type modules to be oriented at various and convenient locations inside the vehicle. It is oftentimes desirable by the automobile manufacturer to have the aforesaid information modules, such as an automatic calibrating compass, clock, temperature and other type modules oriented in locations other than the instrument panel on the dashboard, such as in overhead consoles and the like. Such locations of the information type modules will then provide more space for other modules in either the instrument panel on the dashboard or even in the overhead console. One such location for information type modules is the rearview mirror because it allows for easier viewing of the display without the driver removing his/her eyes from the road. One known unlighted display on an externally mounted rearview mirror is disclosed in U.S. Pat. No. 1,528,082. There, nevertheless, exists problems associated with locating lighted information type modules in a rearview mirror environment. Primarily there would be substantial additional cost to the automobile manufacturer because they would have to run additional wires from the instrument panel on the dashboard to enable the light intensity of the light emitting elements of lighted type information type modules to be controlled so as to render the intensity thereof reduced during nighttime driving, for example, and render them non-distractive to the vehicle driver. Further, if such lighted information type modules are embodied in the rearview mirror environment, the provision of electrochromic layer transmissive attenuation, as described in the aforementioned U.S. Pat. No. 4,917,477, will diminish the light intensity of the light emitting elements during glare conditions. Thus, heretofore, the rearview mirror environment was not deemed to be an appropriate environment for lighted information type modules, especially in mirror constructions embodying electrochromic layer transmissive attenuation capabilities.
Another factor to be considered in orienting a lighted information type display in a rearview mirror environment is that a vacuum fluorescent lighting element would create a problem in safety, namely, the intensity of the vacuum fluorescent display would be distracting to the driver. That is, the readout value of the lighted information type display must be visible through the electrochromic layer as well as be comprehended by the driver. Yet, the display should not be too bright in order to distract the driver's attention from viewing the road forward and rearward. The amount of distraction will increase during nighttime driving because the ratio of light changing from day to night light condition is approximately one million to one, and the display intensity will be immensely brighter to the driver's eyes during the night condition, especially if there is no compensation for the intensity of the information displayed in the rearview mirror setting.
Accordingly, it is an object of this invention to provide a light sensing control system for controlling the intensity of the light emitting elements of the vehicle instrumentation visible to the vehicle operator over a range as a function of light levels so that as the light levels vary, the intensity of the light emitting elements will also vary whereby the instrumentation will remain visible at all times to the vehicle operator, but not at an intensity that would be considered distracting to the vehicle operator during variable light conditions.
Another object of the invention is to provide an improved electro-optic rearview mirror incorporating improved control circuitry whereby the luminance of a light emitting display embodied in the mirror varies with respect to the light transmittance of the electro-optics.
Another object of the invention is to provide an improved electro-optic rearview mirror incorporating improved control circuitry whereby the luminance of a vacuum fluorescent display embodied in the mirror varies inversely with respect to glare light levels impinging on the mirror.
Another object of the invention is to provide an improved electro-optic rearview mirror incorporating improved control circuitry whereby the luminance of a light emitting display embodied in the mirror varies directly with respect to ambient light levels.
Another object of the invention is to provide an improved electro-optic rearview mirror incorporating improved control circuitry whereby the luminance of a light emitting display embodied in the mirror varies inversely with respect to the levels of glare light impinging on the mirror and whereby the luminance of the display may be modified independently of the glare light levels impinging on the mirror.
It is a further object of this invention to provide an ambient light sensing control for varying the intensity of light emitting elements on instrumentation mounted on a rearview mirror assembly of a vehicle.
It is a further object of this invention to provide a light sensing control, as aforesaid, wherein electrochromic means is mounted in front of the light emitting elements of the vehicle instrumentation system so that the light absorption characteristic of the electrochromic means can effect a varying of the intensity of the light emitting elements visible therethrough to the vehicle operator.